| BackgroundAtlas fracture is a common traumatic disease of upper cervical spine. As the atlas is adjacent to one of the most important aspect of brain-medulla, any trauma diseases might make a destruction to it. Then the respiratory system and the circulatory system will lose their normal function. So, we may get the idea that the management of atlas fracture is risky, difficulty and challenging. The orthopedists always use conservative or surgical methods to treat the patients who is suffering the atlas fractures. The conservative ways is more safety than surgery methods, so more doctors choose conservative methods. But the expectant methods may prolong the period of treatment and cause some serious complications. The surgical ways include occipital cervical fusion surgery and atlanto-axial vertebral fusion surgery. They can protect the central and peripheral nerves near the atlas,but they may decrease the motion range of the craniocervical junction in the same time. The concept of physiological fixation is proposed when the orthopedists want to find a way can both regain the stability and preserve the mobility of upper spine. These years,several experts, domestic and overseas, made majority of researches to test the methods of treating atlas fracture with physiological fixation.Some of the surgeons even designed several methods to treat patients. We tried hard and used some new ways to treat our patients, too. In some of the cases, we only fixed the atlas with screws an rods, and most of the patients recovered well. Based on the concepts and the trials, we invented a new system to treat atlas fracture. And we named it the posterior plate-rod system.ObjectivesWe operated on the human cadaver specimens to practice how to fix the atlas with lateral screws and titanium rods as we do in the atlas surgeries. Then based on the results in the operating on the specimens, we redesigned some parts of the system and perfected the details which cannot conform to our requirements. At last, methods of biomechanical analysis was used to test the stability of atlas fracture specimens which is fixed with posterior plate-rod system. Our research is to provide the rationale for clinical use. In the future, we hope to use the system to treat the atlas fractured patients.MethodsPart OneTwo fresh human cadaveric upper cervical spine specimens were harvested. Before we operated on the specimens, the two cadavers were excluded by deformity and tumor in upper spine. Firstly, we dissect the upper spine of them. We practiced the technique of lateral screw on the atlas, ensure that we can do it well and proficiently. Secondly, we reviewed the classification of the atlas fracture and designed how to make the fractured models. We also practiced this on the specimens. After we resected all the skins, muscles and adipose tissues, we fixed the atlas with the posterior plate-rod system. In this way,we wanted to find whether the new system could work well. Specially, we wanted to see whether the plate could adhere to the posterior arch or not.Part TwoSix fresh human cadaveric upper cervical spine specimens were harvested. And all the cadavers were excluded by fracture, deformity or tumor in upper spine. What’s more, they were excluded by osteoporosis with a bone densitometer system. Then we turn the specimens into models and grouped them by five. The five groups were group A(the intact models),group B1(the the posterior arch fractured models),group B2(Jefferson fractured models),group C1(the specimens of group B1 with the posterior plate-rod system) and group C2(the specimens of group B2 with the posterior plate-rod system). All the models were embedded in the polymethyl methacrylate (PMMA). Then the models were respectively tested by three dimensional movements including extension, flexion, left and right lateral bending, left and right axial rotation were tested on the mechanical testing system machine. The testing levels were C0-C1 and C1-C2. The movements were measured by range of motions (ROM),neutral zones(NZ), and stiffness(axial stiffness, bending stiffness, bending stiffness and rotation stiffness included).All the results were expressed by x ±s. All the statistical relationship among the results were analyzed by SPSS 17.0. Means among different status and different groups were analyzed in ANOVA. And that between two different groups were analyzed in q-test. We defined the P<0.05 as statistically significant difference.ResultsPart OneUpper cervical spine include the lower part of the occipital, atlas and axis. The important joint include atlanto-occipital joint and articulatio atlantoepistrophica. The vital ligaments include anterior atlantooccipital membrane, posterior atlantooccipital membrane, anterior atlanto-axial membrane, posterior atlanto-axial membrane and the cruciform ligament of atlas. The enter point of the lateral screw is the place which is 3mm under the top of the posterior arch on the midcourt line of axis lateral mass.Part TwoLevel of C0-C1:ROM, NZ of group B(including B1 and B2) increased and stiffness decreased with statistically significant difference (P<0.05) when compared to group A.ROM, NZ of group C1 decreased and stiffness decreased significantly when compared to group B1 in all the movements (P<0.05) but stiffness increased significantly. Meaningfully decreasing could be seen when compared ROM and NZ of group C2 to group B2 (P<0.05) but stiffness had significantly increase. ROM and NZ of group Cl decreased whereas the stiffness increased when compared with group A, but it was nonsignificant (P>0.05). ROM and NZ of C2 increased nonsignificantly compared to group A (P>0.05).The stiffness of C2 decreased when compared to group A,but it is unmeaningful, either. Level of C1-C2:ROM, NZ of group B(including B1 and B2) increased and stiffness decreased with statistically significant difference (P<0.05) when compared to group A.ROM, NZ of group C1 decreased and stiffness decreased significantly when compared to group B1 in all the movements (P<0.05) but stiffness increased significantly. Meaningfully decreasing could be seen when compared ROM and NZ of group C2 to group B2 (P<0.05) but stiffness had significantly increase. ROM and NZ of group C1 decreased whereas the stiffness increased when compared with group A, but it was nonsignificant (P>0.05). ROM and NZ of C2 increased nonsignificantly compared to group A (P>0.05).The rotation stiffness of C2 decreased while other three types increased when compared to group A,but it is unmeaningful, either (P>0.05)ConclusionsThe test results told us that after treated by the posterior plate-rod system, the stability of fractured atlas regained. What’s more, the flexibility of the atlas is retained. The system is better in treating the Landell I atlas fracture than treating Jefferson fracture. |
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